Bug Description

In Kubuntu 16.04 the scanners were detected by Xsane or other scan programs as soon as it were plugged in. Also, if you unplugged it then plugged in again also Xsane detected it immediately.

But in Kubuntu 18.04 the scanner is not detected by Xsane if you plug in once Kubuntu 18.04 already running. Only it's detected if you starts session with the scanner already plugged in. And if you unplugg it then plug it again it is not detected anymore and you must restart the computer with the cable plugged into the USB, to be detected.

It happens the same thing with other scan programs like Skanlite or Simple Scan.

Also, I just confirmed that although Xsane and other scan programs like Simple Scan and Skanlite detect the scanner (only if it is already plugged in when Kubuntu 18.04 starts), however only Xsane works Ok (except that in this 18.04 version of Kubuntu Xsane program only starts receiving data once the exploration of the document has finished, which makes much slower scanning several documents, as I describe in the Bug #1771520.